GRAVITATION in One Shot - From Zero to Hero || Class 9th

Physics Wallah Foundation・2 minutes read

The session discusses gravity and gravitation, highlighting the Universal Law of Gravitation, Newton's contributions, and the formula for gravitational force. Various examples and practical applications are provided to understand the concepts better and emphasize the importance of studying motion, force, and gravity in a specific order.

Insights

Gravity and fluids are key topics, with the text emphasizing the Universal Law of Gravitation and Newton's contributions to understanding gravity.
The relationship between mass, distance, and gravitational force is detailed, highlighting the formula F = G * (m1 * m2) / r^2 and the significance of understanding acceleration due to gravity.
The text delves into practical examples and applications of gravitational force, such as in satellite communication and navigation.
Pressure, thrust, and weight distribution are explored, showcasing how these factors are interlinked and impact various scenarios, from standing on a mattress to wearing heels.

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Recent questions

What is the Universal Law of Gravitation?
It states gravity exists everywhere, proportional to masses.

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Summary

00:00

Gravity and Gravitation: Laws and Concepts

The session focuses on gravity and gravitation, a part of the JCB Syllabus, with density and relative density being the preceding topics.
Gravity and fluids are discussed in the session, with the latter being the other half of the chapter.
The Universal Law of Gravitation is introduced, emphasizing that gravity exists everywhere in the universe.
Newton's contribution to understanding gravity is highlighted, explaining that gravity is present wherever there is mass.
The gravitational force is described as always attractive and directly proportional to the product of masses and inversely proportional to the square of the distance between them.
The force of gravity is explained to be non-contact, unlike contact forces like friction.
The concept of gravity being attractive in nature is reiterated, with its dependency on mass and distance emphasized.
The Hindi translation of gravity is mentioned, with the term signifying attraction.
The relationship between mass, distance, and gravitational force is detailed, following the Inverse Square Law.
The importance of repetition for concept retention is stressed, encouraging multiple readings, writings, and explanations to solidify understanding.

14:31

Gravitational Force: Law and Calculation Basics

In 12th grade, classes discuss the law of force, stating that it is inversely proportional to the square of the distance between charges or magnetic poles.
The force between charges or magnetic poles is inversely proportional to the square of the distance separating them.
The formula for force between masses or magnetic poles is F = G * (m1 * m2) / r^2, where G is the universal gravitational constant.
The universal gravitational constant, denoted as G, has a value of 6.67 * 10^-11 Newton meter squared per kilogram squared.
The formula for gravitational force between two masses is F = G * (m1 * m2) / r^2, where r is the distance between the centers of the masses.
The gravitational force between two masses on Earth's surface can be calculated using the formula F = G * (m1 * m2) / r^2, with G being 6.67 * 10^-11 and r approximately equal to the radius of the Earth.
The gravitational force exerted by Earth on a 1 kg mass on its surface is approximately 9.8 Newtons, due to the Earth's mass of 6*10^24 kg.
The Earth's gravitational force on an object is equal and opposite to the force exerted by the object on the Earth, following Newton's third law of motion.
The Earth's gravitational force prevents objects from sliding off its surface due to its immense mass and the resulting force it exerts.
The acceleration experienced by an object due to Earth's gravitational force is approximately 9.8 m/s^2, regardless of the object's mass.

30:10

"Gravity's Influence: Flowers to Satellites"

The force of gravity is immense, with a value of 10 to the power of 24.
Flowers are mentioned as a topic of discussion.
The Universal Law of Gravitation is introduced.
The application of the law is explained, focusing on gravity's role in keeping us alive.
The concept of atmosphere and its relation to gravity is discussed.
The impact of gravity on Earth's gases, such as nitrogen, oxygen, and carbon dioxide, is highlighted.
The connection between gravity and high and low tides is explained.
The stability of the solar system due to gravity is emphasized.
Practical numerical examples are provided to understand the effects of changing mass and distance on gravitational force.
The role of gravity in satellite communication and navigation is detailed.

44:06

"Force, Motion, Gravity: Essential Physics Concepts"

Force is essential for acceleration, as explained in the text.
Understanding the relationship between motion and force is crucial.
Gravity plays a significant role in the force and acceleration dynamic.
The text emphasizes the importance of studying motion, force, and gravity together.
Physics topics should be studied in a specific order without skipping any chapters.
The acceleration due to gravity is explained as 9.8 meters per second squared.
The formula for gravitational force is detailed as F = G * (m1 * m2) / r^2.
The acceleration due to gravity formula is derived as G * M / R^2.
The text highlights the significance of understanding acceleration due to gravity for various objects.
The relationship between mass, radius, and gravity is explained in the context of different celestial bodies.

57:58

"Gravity and Acceleration Formulas Explained Simply"

The stomach should be bigger than the planet for the radius to be larger.
High density indicates good gravity on the planet.
Deriving formulas for acceleration due to gravity is a common school question.
Analytical level questions are posed in Olympiad exams.
The formula for acceleration due to gravity on a planet is m/r².
The gravity on a planet is inversely proportional to its radius.
The acceleration due to gravity is 9.8 meters per second squared.
Gravity is greater at the poles compared to the equator due to differences in radius.
The universal gravitational constant is 6.67 x 10^-11 Nm²/kg².
Weight is affected by gravity, with weight being zero at the center of the Earth.

01:15:56

"Gravity, Free Fall, Weight, Mass: Understanding Basics"

Gravity is 9.8 on Earth's surface, but becomes zero at the center of the Earth.
At the Earth's center, gravity becomes zero, leading to weightlessness.
The concept of free fall involves considering only gravitational force and ignoring other forces like air resistance.
In free fall, velocity increases due to acceleration caused by gravity.
A practical example involves calculating the velocity of an object falling from a 120-meter building.
Weight is the force of gravity acting on an object, measured in Newtons (N).
Mass is the amount of matter in an object, measured in kilograms (kg).
Weight can vary based on the gravitational pull, such as on the Moon where it is one-sixth of Earth's gravity.
Understanding the difference between mass and weight is crucial for accurate calculations.
Practice numerical exercises to solidify understanding of concepts like weight and mass.

01:33:13

Forces, Orbits, and Pressure: A Physics Overview

Gravity exerts a force of 600 newtons on a mass of 60 kilograms on Earth.
The discussion shifts to the moon, where a kilogram mass is pulled with 100 newtons.
Kepler's three laws on planetary motion are introduced, predating Newton's laws.
The first law focuses on the elliptical orbit of planets around the sun.
The second law discusses how planets cover equal areas in equal intervals of time.
The third law relates the orbital time period of a planet to its distance from the sun.
Trust is explained as a perpendicular force applied to a surface.
Pressure is introduced as thrust upon an area in contact, measured in Newton per meter squared (Pascal).
Increasing thrust increases pressure, while increasing the area in contact decreases pressure.
Examples illustrate how pressure changes with variations in force and contact area, such as in medical injections.

01:47:50

"Pressure: Force, Area, and Weight Distribution"

Pressure is dependent on force and area.
Weight distribution affects pressure when standing on a mattress.
Standing on a mattress with only feet touching reduces area and increases pressure.
Increasing area reduces pressure, as seen with sitting on a throne.
Wearing heels with small area increases pressure and causes discomfort.
Heavier clothes can also increase pressure on bones and cause deformities.
Animals with wider feet experience less pressure, like camels and elephants.
Pressure increases with depth underwater, affecting objects like pearls.
High pressure can lead to aquarium breakage, as seen in a German incident.
Sharp knife edges reduce pressure, making cutting easier.

01:59:57

"Pressure, Area, and Fluid Dynamics Relationship"

Dividing 100 and 20 by 100 results in 5000, with one digit above and four below.
The value of 625 is discussed, with calculations and comparisons.
Pressure and contact area are linked, affecting the weight distribution.
The concept of pressure increase when an object is allowed to stand is explained.
The difficulty of holding a school bag with a strap made of thin string is discussed.
The importance of broad leaves in holding objects comfortably is highlighted.
The relationship between area, pressure, and fluid dynamics is explained.
The impact of internal forces on fluids, distinguishing between gases and liquids, is detailed.
The concept of pressure exerted by fluids in containers is discussed, emphasizing the continuous nature of this force.
The floating principle is explained, focusing on the balance between buoyant force and weight for objects in fluids.

02:14:56

Archimedes' Principle: Water Displacement in History

Christianity did not exist 2100 years ago, when the Greek Kingdom and Roman Kingdom were prominent.
Archimedes introduced the concept of displacement of water when objects are submerged.
The volume of water displaced is equal to the volume of the object submerged.
Archimedes' principle is utilized in various applications like hydrometers, lactometers, ship manufacturing, submarines, and warships.
The weight of water displaced by an object is equal to the force exerted on the object.
A man sitting in a boat throwing stones into a swimming pool will cause the water level to rise.

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